1. Field of the Invention
The present invention relates to a control device for image blur correction which is applied to an image blur correction device for correcting image blur occurring in an optical equipment, such as a camera.
2. Related Background Art
In existing cameras, because all important photographing operations, such as exposure or focusing operations, are automatically executed, the possibility that failure to perform a desired photographing operation will occur, even by a person not skilled in camera operation, is significantly reduced.
Also, in recent years, a system for preventing hand vibration which is applied to the camera has been studied, and factors that induce photographing error caused by the photographer now have almost been eliminated.
Now, an image blur correction device which prevents hand vibration will be described in brief.
Hand vibration of the camera at the time of photographing normally has a vibration frequency in the range of 1 to 12 Hz. A basic idea for taking a picture without image blur even if such hand vibration occurs at the time of a shutter release is that the vibration of the camera due to hand vibration is detected, and a correction lens is displaced in response to the detected value. Accordingly, in order that a photograph having no image blur can be taken even if the vibration of the camera occurs, it is necessary to first detect vibration of the camera with accuracy and then to correct for image displacement in an optically axial direction due to the hand vibration.
The detection of the vibration (camera vibration) can be theoretically performed by installing in the camera a vibration detection device comprised of a vibration sensor that detects an angular acceleration, an angular velocity, an angular displacement and the like, and a camera vibration detecting circuit that electrically or mechanically integrates the output signals of the vibration sensor so as to output a signal indicating the angular displacement. Then, image blur is corrected by driving a correction optical device that decanters the photographic optical axis on the basis of the above detection information.
Now, an outline of an image blur prevention system having a vibration sensor will be given with reference to FIG. 8. FIG. 8 is a schematic diagram showing an image blur correction device that suppresses image blur caused by a camera vertical vibration 81p and a camera horizontal vibration 81y in a direction indicated by an arrow 81, in the case where the image blur correction device is mounted on an interchangeable lens of a single-lens reflex camera.
In FIG. 8, reference numeral 82 denotes a lens barrel, and 83p and 83y are vibration detection devices which detect the camera vertical vibration and the camera horizontal vibration, respectively, where the respective vibration detection directions are indicated by reference symbols 84p and 84y. Reference numeral 85 denotes a correction optical device (reference symbols 86p and 86y denote coils which give thrust in two directions to the correction optical system 85 in the two directions, respectively, and 87p and 87y are position detecting elements that detect the position of the correction optical device 85 in the two directions, respectively), and the correction optical device 85 is formed with a position control loop and driven with outputs from the vibration detection devices 83p and 83y as desired values so as to ensure stability at an image surface 88.
FIG. 9 is an exploded perspective view showing an example of the structure of the above-described correction optical device 85, which will be described below.
A back surface projected ear 71a of a base plate 71 is inserted into a lens barrel (not shown), and a known lens barrel roller or the like is screwed into a hole 71b so as to be fixed to the lens barrel. A second yoke 72 made of magnetic substance is screwed into a hole 71c of the base plate 71 by a screw that threads through the hole 72a of the second yoke 72, and permanent magnets (shift magnets) 73 such as neodymium magnets are magnetically adsorbed to the second yoke 72. Coils 76p and 76y (shift coils) are inserted into a support frame 75 to which a correction lens 74 is fitted by a C-ring or the like. A first yoke 712 is inserted into positioning holes 712a by respective pins of the base plate 71, and the first yoke 712 is magnetically coupled at its backing surface to the base plate 71 by a magnetic force of the permanent magnets 73.
One end of an L-shaped shaft 711 is inserted into a bearing portion 75d of the support frame 75, and the other end of the L-shaped shaft 711 is inserted into a bearing portion 71d formed in the base plate 71. Also, the shaft 711 is slidably supported only in directions indicated by arrows 713p and 713y with respect to the base plate 71, to thereby regulate the relative rotation (rolling) about the optical axis with respect to the base plate 71 of the support frame 75.
The coils 76p and 76y are located within respective closed magnetic circuits formed of the permanent magnets 73, the first yoke 712 and the second yoke 72. In this arrangement, when a current is permitted to flow in the coil 76p, the support frame 75 is driven in the direction indicated by the arrow 713p, whereas when a current is permitted to flow in the coil 76y, the support frame 75 is driven in the direction indicated by the arrow 713y. 
When the support frame 75 moves on a plane perpendicular to the optical axis, an incident position of a light emitted from light projecting elements 77p and 77y and passing through slits 75ap and 75ay is changed on the position detecting elements 78p and 78y. In general, when the outputs of the position detecting element 78p and 78y are amplified by ICs 731p and 731y and the coils 76p and 76y are driven by the amplified outputs, the support frame 75 is driven so that the outputs of the position detecting elements 78p and 78y are changed. In this example, the-drive directions (polarities) of the coils 76p and 76y are set so that the outputs of the position detecting elements 78p and 78y become small (negative feedback), the support frame 75 is stabilized by the drive forces of the coils 76p and 76y at a position where the outputs of the position detecting elements 78p and 78y become substantially zero.
The above-mentioned method of driving the support frame 75 by negatively feeding back the position detection output is called xe2x80x9cposition control mannerxe2x80x9d, and for example, when a desired value (for example, a hand vibration angle signal) is mixed with the ICs 731p and 731y from an external source, the support frame 75 is extremely faithfully driven in accordance with the desired value.
Actually, the outputs of differential amplifiers 731cp and 731cy are supplied to a main substrate (not shown) through a flexible substrate 716, subjected to A/D conversion and then taken in a microcomputer (not shown).
The A/D converted outputs are appropriately compared with the desired value (hand vibration angle signal) and amplified within the microcomputer, and then subjected to leading phase compensation (for more stabilizing position control) through a known digital filter manner. Thereafter, the signals subjected to the leading phase compensation again pass through the flexible substrate 716, and are then input to an IC 732 (for driving the coils 76p and 76y). The IC 732 conducts known PWM (pulse width modulation) drive on the coils 76p and 76y on the basis of the input signals to drive the support frame 75.
Also, when the correction optical device is not operated, it is necessary to lock the support frame 75. Three projections (not shown) are disposed on a back surface of the support frame 75. The leading edges of those projections are inserted into the inner peripheral surface of a lock ring 719 so that the support frame 75 is fixed. Specifically, when electricity is supplied to a coil 720 through a magnetic circuit consisting of the coil 720 and a lock magnet 718, the lock ring 719 rotates against a lock spring 728, an armature 724 is abutted against an adsorption yoke 729 and electricity is supplied to an adsorption coil 730, as a result of which the armature 724 is adsorbed by the adsorption yoke 729. In this situation, when the supply of electricity to the coil 720 stops, the lock ring 719 is going to return to an original position due to the force of the lock spring 728. However, because the armature 724 is adsorbed by the adsorption coil 729, rotation is regulated, thereby leading to a lock release state. In the case of returning to a lock state, the supply of electricity to the adsorption coil 730 stops so that the lock ring 719 rotates due to the force of the lock spring 728, and the projections of the support frame 75 are inserted into the inner peripheral surface of the lock ring 719, to thereby come to the lock state.
FIG. 10 is a block diagram showing the electric schematic structure of the image blur correction device.
The output of an image blur detection device 2 is processed by a signal processing circuit 3 that executes amplification, high-pass filtering, low-pass filtering and so on, converted into a digital signal by an A/D conversion portion 4 within a microcomputer 1, and then subjected to data processing such as offset removal, high-pass filtering and integration by a data processing portion 5. Also, the output of a position detection device 6 that conducts the position detection of the correction lens is processed by a signal processing circuit 7 that conducts low-pass filtering and so on, converted into a digital signal by an A/D conversion portion 8 within the microcomputer 1 and then subjected to data processing such as amplification by a data processing portion 9. Then, those two signals are calculated by a feedback calculation portion 10 and subjected to amplification and known leading phase compensation by a leading phase compensation portion 11. Then, a drive signal of the correction lens is output to a port of the microcomputer 1, and the correction lens is driven by a correction lens driving device 12 to perform image blur correction.
Also, when image blur correction is not conducted, the correction lens is brought into the lock (engagement) state, whereas when image blur correction is conducted, it is brought into the unlock state. A lock/unlock driving device 13 is designed so as to drive the correction lens.
Then, image blur correction has an optimum characteristic which is adapted to various circumstances such as a case in which a user performs photography while holding a camera by hand or a case in which the user performs photography while the camera is held by a tripod. For example, in the case of a single-lens reflex camera, when the user performs photography while holding the camera by hand, a characteristic of the image blur correction may be set so as to correct even vibration of a low frequency produced by hand vibration. On the other hand, when the user performs photography while the camera is held by a tripod, since no vibration of a low frequency occurs, a characteristic of the image blur correction may be set so as to correct only vibration of a high frequency produced by a quick return mirror and a shutter of the camera. This is because the photographing result is deteriorated by the drifting of a vibration sensor if low frequency correction is effected. In view of this fact, it has been proposed that the support state of the camera be detected, and the image blur correction characteristic be set in accordance with the detected support state.
As one method of detecting the support state of the camera, there is a method of conducting the detection in accordance with a signal level of the vibration sensor. This method is designed so that if the signal level of the vibration sensor within a given period of time is smaller than a predetermined value, the camera holding state is judged as a tripod support state. In this situation, a timing at which the tripod detection starts may be set to the half-depression operation of a release button so as to be synchronized with the photographing intention of the user.
In this example, if the user completely depresses the release button of the camera from a half-depression state to shift the operation to release operation, the mirror and the shutter are driven. However, if such operation is conducted in the tripod support state, the level of the vibration sensor signal is caused to exceed the tripod detection level due to the impact of the mirror and shutter drive, as a result of which there is the possibility that it is detected that the camera is supported by hand, although the camera is in fact supported by a tripod.
Also, in a camera system of the interchangeable lens type, since photographing is enabled without driving a mirror or shutter, depending on the sort of a camera attached to the interchangeable lens having an image blur correction function, it is necessary that the control of tripod detection during photographing is most preferably changed in accordance with the attached camera.
The present invention has been made to solve the above problems associated with the prior art, and therefore has as an object thereof to provide a control device for image blur correction which prevents the operating state of an image blur correction device from being unintentionally changed over due to an influence of a predetermined operation of a camera.
In order to achieve the above object, according to one aspect of the present invention, there is provided a control device for image blur correction which is applied to an image blur correction device that conducts an image blur correcting operation in response to a signal corresponding to an output of a vibration detection sensor, where the control device comprises:
support state judging means which judges whether the device is in a given support state or not, in accordance with the signal corresponding to the output of the vibration detection sensor;
operation state control means which changes the operating state of the image blur correction device in response to the judgement result by the support state judging means so as to set the operating state to a first state, in which the image blur correction device does not conduct the given image blur correcting operation when the support state judging means judges that the device is in the given support state, and to shift the operating state to a second state, in which the image blur correction device conducts the given image blur correcting operation in response to a judgement by the support state judging means that the device is released from the given support state; and
regulating means which regulates the shift of the state from the first state to the second state, when the predetermined operation of the camera starts, in response to a judgement by the support state judging means, which is responsive to the judgement by the support state judging means that the device is released from the given support state.